KR101657546B1 - Apparatus for calibration between robot and displacement sensor and method for calibration using this - Google Patents

Abstract

A calibration apparatus between a robot and a displacement sensor for automatically performing a calibration process and a method using the same are disclosed. The calibration apparatus between the robot and the displacement sensor is for performing a calibration between the robot tool and the displacement sensor for acquiring the one-dimensional distance information by being connected to the robot tool. The calibration tool is moved in parallel relative to the robot tool, And a control unit for controlling the driving of the robot tool so as to measure the position of each vertex of the rectangle in contact with the circle of the measuring jig. Thus, as the calibration process is automated, accuracy and precision are greatly improved and the time required for calibration can be reduced.

Description

Technical Field [0001] The present invention relates to a calibration apparatus between a robot and a displacement sensor, and a calibration method using the same.

The present invention relates to an apparatus and method for calibrating a robot and a displacement sensor, and more particularly, to an apparatus and method for calibrating a position and a shape of a workpiece, And a calibration method using the same.

In order to convert the one-dimensional distance information measured by a distance sensor such as a laser displacement sensor (LDS) into three-dimensional position information for use by the robot, calibration is necessarily preceded.

Conventional calibration work is achieved by repeatedly measuring the reference point, which accurately knows the three-dimensional position, from the sensor at various positions by manually manipulating the robot, and computing the attitude of the robot and the measured value of the sensor inversely.

In other words, in order to perform the calibration, a three-dimensional vector indicating the three-dimensional distance information between the robot tool and the sensor and the measurement direction of the sensor is required. Conventionally, such information is acquired depending on the user's measurement. Therefore, precise manipulation of the robot is required to measure an accurate reference point with the sensor.

However, since the manipulation of the robot by the user's manual operation depends on the skill of the user, high accuracy can not be obtained, reliability of the work is degraded, and work time is increased, which is inefficient.

In addition, there was a risk of accident when a user directly observes a high intensity laser with the naked eye.

In order to solve such conventional problems, the present invention provides a calibration apparatus between a robot and a displacement sensor for automatically performing a calibration process and a method using the same.

The apparatus for calibration between a robot and a displacement sensor according to the present invention is for performing a calibration between a robot tool and a displacement sensor for acquiring one-dimensional distance information by being connected to the robot tool. The calibration tool is relatively moved parallel to the robot tool, And a control unit for controlling the driving of the robot tool so as to measure the positions of the measuring jig and the rectangular vertices in contact with the circle of the measuring jig.

In this case, the measuring jig may be inclined such that the width becomes narrower from the upper part to the lower part.

In addition, the control unit can detect the boundary point by continuously measuring the displacement of the measuring jig while moving the robot tool in the respective axial directions.

In addition, the control unit can use the information of the boundary point detected in the interval in which the measurement distance of the displacement sensor decreases in proportion to the thickness of the measurement jig.

In addition, it is possible to further include a touch sensor that automatically matches the robot tool with the center of the measuring jig.

According to another aspect of the present invention, there is provided a method of calibrating a robot and a displacement sensor, the method comprising: a first step of positioning a disc-shaped measuring jig in parallel with an XY plane of a robot tool center position coordinate system; A third step of detecting a boundary point of each vertex of the rectangle in contact with the circle of the measuring jig using a displacement sensor connected to the robot tool while moving the robot tool in at least one direction of the X axis and the Y axis, A fourth step of moving the robot tool in the Z axis direction and changing the rotation angle; and a fourth step of moving the robot tool in at least one direction of the X axis and the Y axis, A fifth step of detecting a boundary point of each of the vertexes of the robot tool, and a fifth step of detecting a boundary point of each vertex of the robot tool using the coordinates of the robot tool and the displacement sensor measured values obtained by the second, And a sixth step of obtaining a three-dimensional position of the measurement origin of the displacement sensor observed in the measurement direction of the displacement sensor observed in the coordinate system and the robot tool center position coordinate system.

In this case, after the second step, moving the robot tool in the Z-axis direction may be further included.

Further, the measuring jig may be inclined such that its width becomes narrower from the upper part to the lower part.

In the third step, the robot tool is moved in at least one direction of the X-axis and the Y-axis, the descending boundary point is detected using the displacement sensor, the robot tool is moved in the other direction, Can be searched.

The second step includes the steps of positioning the robot tool on the measurement jig, measuring at least three points on the measurement jig with the touch sensor, and calculating the rotation angle of the robot tool using the result measured with the touch sensor Measuring a rectangle in contact with the measuring jig after the robot is fixed by using a touch sensor; and moving the robot tool such that the XY plane of the robot tool center position coordinate system is parallel to the measuring jig and the center of the measuring jig matches the robot tool Step < / RTI >

According to the present invention, as the calibration process is automated, the accuracy and precision are greatly improved and the time required for calibration can be reduced.

In addition, since the user does not visually observe a high-intensity laser, work safety is improved.

1 is a perspective view of a calibration apparatus according to an embodiment of the present invention,
2 is a perspective view of a measuring jig according to an embodiment of the present invention,
3 is a flow chart of a calibration method according to an embodiment of the present invention,
FIG. 4 illustrates a structure of a displacement sensor according to an embodiment of the present invention,
FIG. 5 illustrates a three-dimensional positional relationship between a robot tool and a displacement sensor according to an embodiment of the present invention,
FIG. 6 illustrates a calibration process between a robot tool and a displacement sensor according to an embodiment of the present invention,
7A and 7B illustrate an automatic calibration process according to an embodiment of the present invention,
FIG. 8 illustrates a process of detecting a boundary point of a measurement jig according to an embodiment of the present invention,
9A and 9B illustrate the operation of the inclined surface of the measuring jig according to the embodiment of the present invention,
10A to 10E illustrate a process of automatic calibration according to an embodiment of the present invention,
11A to 11E illustrate a process of automatic calibration using a touch sensor according to an embodiment of the present invention.

Hereinafter, the technical configuration of the calibration apparatus between the robot and the displacement sensor will be described in detail with reference to the accompanying drawings.

1 is a perspective view of a calibration apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the calibration apparatus performs calibration between the robot tool 10 and the displacement sensor 20. The displacement sensor 20 is connected to the robot tool 10 to obtain one-dimensional distance information.

Such a calibration apparatus includes a measurement jig 30, and a control unit (not shown).

The measuring jig 30 is moved in parallel relative to the robot tool 10, and is formed in a disc shape.

The control unit controls the driving of the robot tool 10 so as to measure the position of each vertex of the rectangle in contact with the circle of the measuring jig 30. [ In this case, reference numeral 31 denotes a path along which the laser spot of the displacement sensor 20 moves when measuring a rectangle in contact with the upper surface of the measuring jig 30, and reference numeral 11 denotes a robot tool 10 It is a moving path.

Consequently, it becomes possible to automatically perform the calibration through the configuration of the measuring jig 30 and the control unit. Details of this principle and description will be described later.

2 is a perspective view of a measuring jig according to an embodiment of the present invention.

Referring to FIG. 2, it is preferable that the measuring jig 30 is formed with a sloped surface 35 on its side surface. The inclined surface 35 is formed to be inclined so as to be narrower from the upper portion of the measuring jig 30 to the lower portion thereof.

It is also preferable that the control unit detects the boundary point by continuously measuring the displacement of the robot tool 10 with the displacement jig 30 while moving the robot tool 10 in each axis direction.

It is preferable that the control unit use the information of the boundary point detected in the interval in which the measurement distance of the displacement sensor 20 decreases in proportion to the thickness of the measurement jig 30. [

In addition, the calibration device may further include a touch sensor (not shown). The touch sensor has a function of automatically matching the robot tool 10 to the center of the measuring jig 30 and can be mounted on the robot tool 10. [

The effect of the configuration of such a calibration apparatus will be described in detail in connection with a calibration method to be described later.

3 is a flow chart of a calibration method in accordance with an embodiment of the present invention.

1 to 3, the calibration method includes a first step (S10) of positioning the measuring jig 30 in parallel with the XY plane of the center position coordinate system of the robot tool 10, And a displacement sensor 20 connected to the robot tool 10 while moving the robot tool 10 in at least one of X and Y axes A third step (S30) of detecting a boundary point of each vertex of a rectangle in contact with the circle of the measuring jig (30), a fourth step (S30) of moving the robot tool (10) The robot tool 10 is moved in at least one direction of the X axis and the Y axis and the boundary point of each vertex of the rectangle in contact with the circle of the measuring jig 30 is detected using the displacement sensor 20 The coordinate and displacement of the robot tool 10 obtained by the fifth step S50 and the second step S20, the third step S30 and the fifth step S50, respectively, The measurement direction of the displacement sensor 20 observed in the center position coordinate system of the robot tool 10 and the measurement origin of the displacement sensor 20 observed in the center position coordinate system of the robot tool 10 And a sixth step (S60) of acquiring the dimensional position.

In this case, it is preferable to further include moving the robot tool 10 in the Z-axis direction after the second step S20.

Also, the measuring jig 30 preferably has a side inclined so that its width becomes narrower from the upper part to the lower part.

The third step S30 is to move the robot tool 10 in at least one of the X axis and the Y axis while searching for the descending boundary point using the displacement sensor 20 and then the robot tool 10 It is preferable to search for the rising boundary point by using the displacement sensor 20. [

The second step S20 includes positioning the robot tool 10 on the measurement jig 30 and measuring at least three points on the measurement jig 30 with a touch sensor (not shown) Measuring a rectangle in contact with the measuring jig 30 after fixing the rotation angle of the robot tool 10 by using a result measured by the touch sensor and measuring the rectangle in contact with the XY And moving the robot tool 10 such that the plane is parallel to the measuring jig 30 and the center of the measuring jig 30 and the robot tool 10 coincide with each other.

Now, principles and effects of the calibration apparatus and method according to one embodiment of the present invention will be described in detail.

4 illustrates a structure of a displacement sensor according to an embodiment of the present invention.

Referring to FIG. 4, the displacement sensor 20 according to an embodiment of the present invention may be implemented as a laser displacement sensor (LDS). LDS uses optical triangulation to measure the distance between a sensor and an object. A laser diode 21 and a light receiving unit 22 are formed in the displacement sensor 20.

The position of the laser reflected light measured by the light receiving section 22 changes in accordance with the change of the distance between the object 90 (91) and the laser diode 21. [ Consequently, by using the position of the laser reflected light measured by the light receiving section 22, the distance between the object 90 (91) and the laser diode 21 can be calculated inversely.

FIG. 5 illustrates a three-dimensional positional relationship between a robot tool and a displacement sensor according to an embodiment of the present invention.

For convenience of explanation, the displacement sensor 20 is represented by LDS and uses the same reference numerals. The measured value of the LDS 20 is one-dimensional distance information. In order to use this information, it is necessary to convert it into three-dimensional position information. It is noted that the LDS 20 can be fixedly used to the robot tool 10, or can be installed separately. In this embodiment, the LDS 20 is fixed to the robot tool 10. In this case, the points measured by the LDS 20 can be converted into three-dimensional coordinates through the following process.

는 Base 좌표계에서 관측한 TCP 좌표계의 원점의 위치가 기록된 3차원 벡터이며,

는 Base 좌표계에서 관측한 TCP 좌표계의 회전 정보가 기록된 3×3 회전 변환 행렬이다.In this case, the Base coordinate system is fixed to the ground as a coordinate system used by the robot tool 10, and the TCP (Tool Center Position) coordinate system is a coordinate system fixed to the robot tool 10.

Is a three-dimensional vector in which the position of the origin of the TCP coordinate system observed in the base coordinate system is recorded,

Is a 3 × 3 rotation transformation matrix in which rotation information of the TCP coordinate system observed in the base coordinate system is recorded.

와

는 로봇의 기구학을 통해 쉽게 계산할 수 있다. D는 LDS(20)의 측정값이며, P_LDS 와 P₀ 간의 거리를 의미한다. ^TCPu 는 TCP 좌표계에서 관측한 LDS(20)의 측정 방향을 나타내는 단위 벡터이며,

는 TCP 좌표계에서 관측한 LDS(20)의 측정 원점의 3차원 위치이다.therefore,

Wow

Can be easily calculated through the kinematics of the robot. D is the measured value of the LDS 20, which means the distance between P _LDS and P ₀ . ^TCP u is a unit vector indicating the measurement direction of the LDS 20 observed in the TCP coordinate system,

Dimensional position of the measurement origin of the LDS 20 observed in the TCP coordinate system.

FIG. 6 illustrates a calibration process between a robot tool and a displacement sensor according to an embodiment of the present invention.

는 LDS(20)가 로봇 툴(10)에 대해 어떻게 장착되어 있는지를 묘사하는 변수들로서 그 자세한 관계는 도 6에 도시된 바와 같다. P_LDS 는 LDS(20)의 측정 원점, 즉 D가 0인 점을 나타내며 u는 LDS(20)의 레이저 투사선과 일치하는 크기가 1인 방향 벡터로서 LDS(20)의 측정 각도를 나타낸다. ^TCP u and < RTI ID = 0.0 >

Are variables that describe how the LDS 20 is mounted to the robot tool 10, and the detailed relationship thereof is as shown in Fig. P _LDS denotes a measurement origin of the LDS 20, that is, a point where D is zero, and u denotes a measurement angle of the LDS 20 as a direction vector having a size equal to the laser projection line of the LDS 20.

The values of these two variables are not always constant, but are changed by collisions, vibrations, heat, and the like that occur while using the robot. Therefore, it is necessary to measure and correct the value from time to time. After repeatedly measuring the LDS 20 in various postures using the LDS 20, the measurement attitude of the robot and the measured value of the LDS 20 are converted into [Equation 1] (Least Square Sense).

As a result, the calibration apparatus and method according to the present invention can improve the precision and accuracy of calibration and minimize the time loss by automating the calibration process between the robot and the LDS.

7A and 7B illustrate an automatic calibration process according to an embodiment of the present invention.

Referring to FIGS. 7A and 7B, the measuring jig 30 has a circular shape in a plane, and performs automatic calibration using one circle and two rectangles which are in contact with the circle. A rectangle tangent to a circle must have its center coincident with the center of the circle, and the length of its diagonal line coincides with the diameter of the circle. Therefore, since the lengths of the rectangles shown in Fig. 7A and the diagonal lines shown in Fig. 7B are the same, the following equations are established.

Further, when selecting the internal coordinate system coincides with the center of the origin is cool and such that the axes are parallel to the sides of a rectangle, the coordinates of each vertex of the rectangle by using only two parameters, x _da and y _da or x _db and y _db Can be expressed. The expression is expressed as follows.

As a result, by measuring the area corresponding to each vertex of the rectangle using the LDS, it is possible to calculate the inverse of the measurement angle and the mounting position of the LDS.

FIG. 8 illustrates a process of detecting a boundary point of a measurement jig according to an embodiment of the present invention.

In order to measure a rectangle in contact with the measuring jig 30, a boundary point is detected by moving the robot in each axis direction while continuously measuring the LDS 20 as shown in Fig. In the vicinity of the boundary points the measurement value of the LDS (20) D ₁ - therefore changing to a> D _2, it is possible to readily detect a boundary point. There are two boundary points, the rising boundary point shown on the left side of FIG. 8 and the falling boundary point shown on the right side of FIG. 8, and the boundary point used for calibration is preferably the value of the rising boundary point. Since the descending boundary point can be detected immediately after the boundary point, the measurement accuracy is lower than the rising boundary point.

9A and 9B illustrate the action of the inclined surface of the measuring jig according to an embodiment of the present invention.

Now, the reason why the inclined surface should be formed on the side surface of the measuring jig will be explained. If the LDS 20 is inclined and mounted, as shown in FIG. 9A, if there is no? In the measuring jig 30 ', the measured values of the LDS 20 before and after the boundary point continuously change, . However, if? Exists in the measurement jig 30 as shown in FIG. 9B, accurate boundary points can be detected even if the LDS 20 is inclined.

Now, the calibration method will be described in more detail through a preferred embodiment.

10A to 10E illustrate a process of automatic calibration according to an embodiment of the present invention.

First, the measuring jig 30 is positioned in parallel with the XY plane of the robot TCP coordinate system. Then, the robot tool 10 is made to coincide with the center of the measuring jig 30. The coordinates of a robot tool (10) will be referred to as T _0.

Thereafter, the robot tool 10 is moved a certain distance in the + Z direction in order to prevent collision between the robot tool 10 and the measurement jig 30 in the measurement motion.

Thereafter, the robot tool 10 is moved in parallel in the + X and + Y directions, and the LDS 20 is used to search for a descending boundary point. Then, the robot tool 10 is moved at a low speed in the -Y direction while the LDS 20 is used to accurately detect the rising boundary point. The coordinate system of the robot tool 10 for measuring the detected boundary point is P _1a , the coordinate system of the robot tool 10 is T _1a , and the measured value of LDS (20) is D _1a .

Thereafter, while the robot tool 10 is moved in parallel to the -Y direction, the LDS 20 is used to search for a descending boundary point. Then, the robot tool 10 is moved at a low speed in the + Y direction while the LDS 20 is used to accurately detect the rising boundary point. The detected boundary point is P _2a , the coordinate system of the robot tool 10 for measuring the boundary point is T _2a , and the measured value of LDS (20) is D _2a .

Thereafter, the robot tool 10 is moved in parallel to the -X direction while using the LDS 20 to search for a descending boundary point. Then, the robot tool 10 is moved at a low speed in the + X direction while the LDS 20 is used to accurately detect the rising boundary point. The detected boundary point is P _3a , the coordinate system of the robot tool 10 for measuring the boundary point is T _3a , and the measured value of LDS (20) is D _3a .

Thereafter, the robot tool 10 is moved in parallel in the + Y direction while the LDS 20 is used to search for a descending boundary point. Then, the robot tool 10 is moved at a low speed in the -Y direction while the LDS 20 is used to accurately detect the rising boundary point. The detected boundary point is P _4a , the coordinate system of the robot tool 10 for measuring the boundary point is T _4a , and the measured value of the LDS (20) is D _4a .

After this process, the robot tool 10 is moved by a predetermined distance in the + Z direction, and the rotation angle of the robot tool 10 is changed by a certain angle. Thereafter, the process of detecting the boundary points P _1a to P _4a described above is repeated. At this time, as the measured feature points, respectively _{P 1b, P 2b, P 3b} , P 4b and, and the coordinate system of the robot tool (10) for measuring the boundary point that each T _1b, T _2b, T _3b, T _4b, LDS ( 20) measurement values are referred to as D _1b , D _2b , D _3b , and D _4b , respectively.

T ₀ , T _1a to T _4a , T _1b to T _4b , D _1a to D _4a , and D _1b to D _4b can be obtained through the above process. [Equation 1] and [Equation 2] are re-induced corresponding to the process of detecting the P _1a boundary point among the above steps.

The decomposition of the expression for this derived vector yields three scalar equations with eight variables as follows.

또는

or

In the above process, all the robot tools 10 move in parallel, so that the following relationship holds.

(1≤i≤4)

(1? I? 4)

By repeating this procedure for all measurement results, the following equation can be obtained.

와

의 모든 계산을 수행할 수 있다.The matrix A in the above equation can be calculated because the coefficient of the matrix is always equal to the number of columns of the x vector when D _a does not coincide with D _b . Therefore, the calibration variable

Wow

Can be performed.

therefore,

의 관계가 성립된다.

.

11A to 11E illustrate a process of automatic calibration using a touch sensor according to an embodiment of the present invention.

The touch sensor automatically aligns the robot tool 10 with the center of the measuring jig 30. The process will be described in detail as follows.

First, the robot tool 10 is placed on the measurement jig 30. Thereafter, as shown in FIG. 11A, three points are measured with the touch sensor on the measuring jig 30. FIG. These points are referred to as P _t1 , P _t2 , and P _t3 , respectively.

Using the measurement results, we select the object coordinate system as shown in the following equation and calculate the relation with the TCP coordinate system.

와 일치시킨 뒤, 도 11a 내지 도 11e에 도시된 바와 같이 측정용 지그(30)에 내접하는 직사각형을 터치 센서로 측정한다. 이 경우, 각 꼭지점을 P_t4 ~ P_t7이라 한다.Thereafter, the rotation angle of the robot tool 10

11A to 11E, a rectangle in contact with the measuring jig 30 is measured with a touch sensor. In this case, each vertex is referred to as P _t4 to P _t7 .

Then, referring to the following equation, the robot tool 10 is moved such that the XY plane of the TCP coordinate system is parallel to the measuring jig 30 and the center thereof coincides with the robot tool 10.

,

,

,

,

(4≤i≤7)

(4? I? 7)

Although the calibration apparatus between the robot and the displacement sensor and the calibration method using the same have been described with reference to the embodiments shown in the drawings, the present invention is merely illustrative and any person skilled in the art can make various modifications and equivalent other embodiments . Accordingly, the scope of the true technical protection should be determined by the technical idea of the appended claims.

10: Robot tool 20: Displacement sensor
30: Measuring jig

Claims (10)

A method for performing calibration between a robot tool and a displacement sensor connected to the robot tool to obtain one-dimensional distance information,
A measurement jig that is moved in parallel relative to the robot tool and formed in a disk shape; And
And a controller for controlling the driving of the robot tool so as to measure a position of each vertex of the rectangle in contact with the circle of the measuring jig. The method according to claim 1,
Wherein the measuring jig has a side inclined so that the width gradually decreases from the upper portion to the lower portion. The method according to claim 1,
Wherein the control unit continuously measures the jig with the displacement sensor while moving the robot tool in each axial direction to detect a boundary point. The method of claim 3,
Wherein the control unit uses the information of the boundary point detected in a section in which the measurement distance of the displacement sensor decreases in proportion to the thickness of the measurement jig. The method according to any one of claims 1 to 4,
Further comprising a touch sensor for automatically matching the robot tool to the center of the measuring jig. A first step of positioning a disk-like measuring jig in parallel with the XY plane of the robot tool center position coordinate system;
A second step of aligning the robot tool with the center of the measuring jig;
A third step of detecting a boundary point of each vertex of a rectangle in contact with a circle of the measuring jig using a displacement sensor connected to the robot tool while moving the robot tool in at least one direction of an X axis and a Y axis;
A fourth step of moving the robot tool in a Z-axis direction and changing a rotation angle;
A fifth step of detecting a boundary point of each vertex of a rectangle in contact with a circle of the measuring jig using the displacement sensor while moving the robot tool in at least one direction of an X axis and a Y axis; And
Measuring a position of the displacement sensor in the robot tool center position coordinate system and a measurement direction of the displacement sensor measured in the robot tool center position coordinate system using the coordinates of the robot tool and the displacement sensor measurement values obtained by the second, And a sixth step of obtaining a three-dimensional position of the measurement origin of the displacement sensor, which is observed in the tool center position coordinate system. The method of claim 6,
Further comprising moving the robot tool in the Z-axis direction after the second step. The method of claim 6,
Wherein the measuring jig has a side inclined such that the width gradually decreases from the upper portion to the lower portion. The method of claim 6,
In the third step,
The robot tool is moved in at least one direction of the X axis and the Y axis and the descending boundary point is searched using the displacement sensor and the robot tool is moved in the other direction to detect a rising edge point using the displacement sensor And a displacement sensor for detecting a displacement between the robot and the displacement sensor. The method of claim 6,
Said second step comprising:
Positioning the robot tool on the measurement jig;
Measuring at least three points on the measurement jig with a touch sensor;
Measuring a rectangle in contact with the measurement jig using the touch sensor after fixing the rotation angle of the robot tool using the measurement result with the touch sensor; And
And moving the robot tool such that the XY plane of the robot tool center position coordinate system is parallel to the measuring jig and the center of the measuring jig and the robot tool coincide with each other. Way.

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